固体浸没透镜用于飞秒三维光存储研究

为进一步提高光存储密度，利用固体侵没透镜（SIL）与数值孔径为0.55的长工作距离物镜对飞秒激光脉冲进行聚焦，完成了PMMA及石英介质上的存储实验,并对聚焦物镜焦点与SIL底面离焦时的介质内焦点位置和系统的数值孔径进行了模拟。实验结果表明：当聚焦物镜焦点与SIL底面适当离焦时，实际聚焦在介质内的焦点深度不断加深，且系统的有效数值孔径不断增大。利用这一结果，在距PMMA表面20μm的地方得到了点间距1μm，层间距2.5μm的6层空间点阵；在距石英介质表面15μm的地方获得了点间距为0.6μm，层间距为2.5μm的5层空间点阵，其存储密度可达1.1×1012bits/cm3。     

基于介电常数近零态和铟锡氧化物集成硅基波导的电光半加器

为了解决传统电光混合运算逻辑单元速率低、功耗高、尺寸大等问题,以实现电光混合高速运算,本文设计了一种基于介电常数近零态(Epsilon-Near-Zero)和铟锡氧化物(ITO)薄膜电调控的集成硅基波导电光混合半加器。利用ITO激活材料薄膜的电调控特性实现了光路通断和交叉,从而实现了两位二进制数的半加法功能,通过3D-FDTD模拟仿真对器件模型结构参数进行了优化设计。仿真实验结果表明,当施加电压为0 V和2.35 V时,器件能够完成光信号逻辑控制。电光混合半加器工作在1 550 nm波长时,其插入损耗为0.63 dB,消光比为31.73 dB,数据传输速率为61.62 GHz,每字节消耗能量为13.44 fJ,整个半加器尺寸小于21.3μm×1.5μm×1.2μm。该器件具有结构紧凑、插入损耗低等特点,为高速电光混合光学逻辑器件及半加器设计提供了理论依据。     

中红外宽带消色差超透镜的设计

中红外热成像系统是通过探测物体本身的辐射进行成像，不需要外部光源。而传统的中红外热成像系统体积大，不利于小型化。本文基于传输相位理论，采用时域有限差分（FDTD）法，使用FDTD软件计算仿真，探究了不同的单元半径、纳米柱高度及单元周期对相位延迟及透过率的影响，并且针对不同的纳米柱半径，利用传输相位调控实现中红外（3～5μm）波长下全介质硅材料的宽带消色差超透镜设计。其数值孔径为0.24，仿真焦距值为147.3μm，半峰全宽（FWHM）为8.11μm，透镜透过率达到70%。设计的超透镜不仅体积小、质量轻、全波长聚焦效率可达到54%，而且为平面透镜，因此易于光学系统集成，在红外成像、红外夜视仪、红外遥感等技术中展现出广阔的应用前景。     

基于F-P腔的极化聚合物的纵向电光调制

利用Fabry-Perot腔实现了置于腔内的极化聚合物电光薄膜的纵向电光调制,此模型中极化电场方向、调制电场方向均与通光方向平行.腔的精细因子大约为18(对1.3μm的光),膜厚度为1μm.实验所得调制深度在调制电场为1V/μm时为0.012%.其结果证实了利用Fabry-Perot腔实现纵向电光调制并利用其研究极化聚合物薄膜的可能. 关键词： 电光效应 激光束调制 光学聚合物 光学设备     

畴反转结构片状集成4×4电光开关的设计与仿真

基于铁电体畴反转结构的电光偏转特性,设计了一种片状集成的4×4电光开关,其由四个结构相同的半抛物和四个抛物形微小偏转器集成构成.通过优化抛物形偏转器结构,给出了电光开关的设计参量,电光开关性能通过光束传播法进行仿真模拟,仿真结果表明该开关切实可行.实际应用中,系统误差可以通过电场调节补偿,使光路准确交换.该片状电光开关的整体尺寸为48 mm×2.2mm×0.5 mm(长×宽×高),最大使用电场约13.73 V/μm,适用于高速交换的光互连系统.     

新型极化聚合物薄膜电光调制器研究

用对硝基偶氮苯类为侧链的键合型聚合物，采用高温电晕极化的方法制作电光薄膜，设计并构造极化聚合物薄膜电光调制器。当通光方向和极化方向平行并且垂直于极化聚合物薄膜的表面时，利用法布里-帕罗（F-P）腔中多光束干涉，可以把通过的光由位相调制转化为强度调制，有利于电光调制器的小型化和高速封装。用这种聚合物薄膜电光调制器测量了锢锡氧化物共面波导上的电信号，并对系统的工作原理进行了分析。实验结果表明，薄膜调制器具有线性电光效应；当F-P腔的精细因子为20（为1.3μm的光），调制电场为1V/μm时，研制的极化聚合物电光调制器的调制深度可达到0.01%。     

砷化镓高速集成电路内部电信号的光探针直接取样

本文介绍了电光取样技术原理报道了砷化镓高速集成电路内部电信号在片直接电光取样测量系统,它的时间分辨率优于20ps,空间分辨率优于3μm.通过对砷化镓共面波导的测量证实该系统可以对砷化镓高速集成电路内部电信号进行在片直接电光取样测量。     

畴反转结构片状集成4×4电光开关的设计与仿真

基于铁电体畴反转结构的电光偏转特性,设计了一种片状集成的4×4电光开关,其由四个结构相同的半抛物和四个抛物形微小偏转器集成构成.通过优化抛物形偏转器结构,给出了电光开关的设计参量,电光开关性能通过光束传播法进行仿真模拟,仿真结果表明该开关切实可行.实际应用中,系统误差可以通过电场调节补偿,使光路准确交换.该片状电光开关的整体尺寸为48 mm×2.2 mm×0.5 mm(长×宽×高),最大使用电场约13.73 V/μm,适用于高速交换的光互连系统.     

施加电场的半抛物量子阱中的电光效应

利用量子力学中的紧致密度矩阵方法，研究了施加电场的半抛物量子阱中的电光效应。通过位移谐振子变换，得到了系统中的电子态的精确解。对典型的GaAs材料进行数值计算的结果表明，随着电场强度的增加，电光效应系数几乎线性随之增加；但是随着半抛物量子阱受限势频率的增加，电光效应系数单调地减小；而且在同样的电场强度及抛物束缚势频率作用下，半抛物量子阱模型中的电光效应系数比抛物量子阱模型中的值大两个数量级，这是由于我们所选模型本身的非对称性以及电场进一步使这种非对称性增强的缘故。     

调平聚焦伺服控制系统的优化设计

以提高共焦差动并行激光直写中光束刻写质量为目标,分析设计了调平聚焦伺服控制系统。采用柱面镜作为像散元件,与四象限光电探测器结合,利用差动像散检测方法和比例积分微分(PID)反馈算法减少光源和外部干扰的误差,获得高灵敏度、高精度、高稳定性的探测曲线。通过优化光学设计参数,本系统能获得具有高灵敏性与一致稳定性的探测曲线,探测范围为3μm,静态聚焦误差可达±5.0nm;动态聚焦压电陶瓷(PZT)伸长量可保证在焦深范围内,焦点位置辨别精度可达纳米量级,可探测调平台的倾斜角和俯仰角在0.01mrad左右。利用该系统可实现光栅的刻写,进一步为更大尺寸、更高密度的光栅刻写提供依据。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.